James Serra notes that there is a free one-month trial of Azure SQL Data Warehouse:
You can use this one month free trial to do POCs and try out SQL DW up to 200 DWU and 2TB of data. You must sign up by December 31st 2016. Please note that once the one month free trial is over, you will start getting billed at general availability pricing rates. For more information on the free trial, and to sign up, go here.
This is great because you can quickly run out of credits otherwise.